NetBSD/lib/librt/shm.c

137 lines
3.5 KiB
C

/* $NetBSD: shm.c,v 1.1 2013/12/19 19:11:50 rmind Exp $ */
/*-
* Copyright (c) 2013 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Mindaugas Rasiukevicius.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Interface for POSIX shared memory objects.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: shm.c,v 1.1 2013/12/19 19:11:50 rmind Exp $");
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <limits.h>
/*
* Shared memory objects are supported using tmpfs.
*/
#define SHMFS_DIR_PATH "/var/shm"
#define SHMFS_DIR_MODE (S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
#define SHMFS_OBJ_PREFIX ".shmobj_"
#define MOUNT_SHMFS MOUNT_TMPFS
static const char * _shmfs_path = NULL;
static bool
_shm_check_fs(void)
{
const char *shmfs = SHMFS_DIR_PATH;
struct statvfs sv;
struct stat st;
if (statvfs1(shmfs, &sv, ST_NOWAIT) == -1) {
return false;
}
if (strncmp(sv.f_fstypename, MOUNT_SHMFS, sizeof(sv.f_fstypename))) {
return false;
}
if (lstat(shmfs, &st) == -1) {
return false;
}
if ((st.st_mode & SHMFS_DIR_MODE) != SHMFS_DIR_MODE) {
return false;
}
_shmfs_path = shmfs;
return true;
}
static bool
_shm_get_path(char *buf, size_t len, const char *name)
{
int ret;
if (__predict_false(!_shmfs_path) && !_shm_check_fs()) {
errno = ENOTSUP;
return false;
}
/*
* As per POSIX: the name should begin with a slash character.
* We may disallow other slashes (implementation-defined behaviour).
*/
if (*name++ != '/' || strchr(name, '/') != NULL) {
errno = EINVAL;
return false;
}
ret = snprintf(buf, len, "%s/%s%s",
_shmfs_path, SHMFS_OBJ_PREFIX, name);
if ((size_t)ret >= PATH_MAX) {
errno = ENAMETOOLONG;
return false;
}
return ret != -1;
}
int
shm_open(const char *name, int oflag, mode_t mode)
{
char path[PATH_MAX + 1];
if (!_shm_get_path(path, sizeof(path), name)) {
return -1;
}
return open(path, oflag | O_CLOEXEC | O_NOFOLLOW, mode);
}
int
shm_unlink(const char *name)
{
char path[PATH_MAX + 1];
if (!_shm_get_path(path, sizeof(path), name)) {
return -1;
}
return unlink(path);
}